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LINQ bug (ConcatNIterator.ToArray()?) #7696
Description
Steps to Reproduce
using System;
using System.Collections.Generic;
using System.Linq;
public static class Program
{
public static void Main()
{
var slots = GetSlots().Concat(new[] { new Slot("q") });
var flatten = slots.Flatten(container => container.AllParentSlots)/*.Select(i => i)*/.ToArray();
var str = string.Join(", ", flatten.Select(x => x == null ? "NULL" : x.Id));
Console.WriteLine(str);
// Mono 5.x including master:
// "a, b, c, d, e, f, g, q, x, NULL"
// .NET, .NET Core, Mono 4.2:
// "a, b, c, d, e, f, g, q, x, y"
}
public class Slot
{
public readonly string Id;
public Slot(string id) => Id = id;
public SlotsHolder ContainedSlotsHolder;
public IEnumerable<Slot> AllParentSlots => ContainedSlotsHolder == null ? new Slot[0] : ContainedSlotsHolder.Slots;
}
public class SlotsHolder
{
public Slot[] Slots;
}
static IEnumerable<T> Flatten<T>(this IEnumerable<T> e, Func<T, IEnumerable<T>> f)
=> e.Concat(e.SelectMany(c => f(c).Flatten(f)));
static IEnumerable<Slot> GetSlots()
{
yield return new Slot("a");
yield return new Slot("b");
yield return new Slot("c");
yield return new Slot("d");
yield return new Slot("e");
yield return new Slot("f");
yield return new Slot("g") {
ContainedSlotsHolder = new SlotsHolder { Slots = new[] {
new Slot("x"),
new Slot("y")
}}};
}
}It feels like the issue is somewhere in ConcatNIterator.ToLazyArray
Current Behavior
The code prints a, b, c, d, e, f, g, q, x, NULL
Expected Behavior
The code should print a, b, c, d, e, f, g, q, x, y just like .NET/.NET Core do.
On which platforms did you notice this
[ ] macOS
[ ] Linux
[x] Windows
Version Used:
mono 5.0-5.13
Does not reproduce on old versions of mono when we had a "slow" Enumerable.ToArray implementation.
Activity
mderoy commentedon Mar 21, 2018
This is affecting Unity users as well:
https://issuetracker.unity3d.com/issues/certain-linq-combinations-yield-wrong-results-on-net-4-dot-6
Bump corefx to bring a fix for mono#7696
Bump corefx to bring a fix for mono#7696
Bump corefx to bring a fix for mono#7696
KosmicTask commentedon Mar 22, 2018
Not sure if this is the same issue but it may have a connection.
The following Distinct() method call succeeds on .Net but raises with a Null ref exception on Mono macOS 10.13
.
var orders = items.SelectMany(e => e.Deductions).Select(e => e.Order).Distinct();
foreach (var order in orders) {
… // order is Null here and raises
}
On Mono
orderis Null thoughordersis an instance of System.Linq.Enumerable.DistinctIterator.In the local vars browser
ordersIEnumerator is Null.Sorry I don't have a test case. It's something that turned up on production code.
Bump corefx to bring a fix for #7696
Bump corefx to bring a fix for #7696
Bump to mono/2017-12/beb137dd
Bump corefx to bring a fix for #7696
marek-safar commentedon Mar 23, 2018
The issue was resolved.
@mugginsoft please test it with mono master or include full test case I could try to test.
KosmicTask commentedon Mar 23, 2018
Will do. If my issue persist I will try and pull it out of its production context.
Bump to mono/2017-12/10758249
KosmicTask commentedon Mar 24, 2018
So I tried the nightly build that includes this fix in my production code and too many things break before I can get anywhere near exercising this particular issue. Will try and pull out a test case.
Bump to mono/2017-12/10758249 (#1471)
Bump to mono/mono:2018-04@f3a2216b (#1503)
Bump to mono/mono:2018-04@f3a2216b (#1503)